Electric motor construction

ABSTRACT

This invention relates to brush actuating mechanisms for direct current motors and, more particularly, to an innnovative plasticmolded housing for these motors. The invention discloses a plastic-molded housing, closed at one end and apertured at the other end, said closed end having opposed longitudinal recesses for receiving a brush, a cam lever, and a helical spring, respectively therein, positively retained by an end cover slipped over said closed end and secured thereto, while said apertured end provides for the insertion of permanent magnets and a driven shaft carrying an armature, and commutator.

ilnited States Patent 91 Wisniewski 51 May 22, 1973 1 ELECTRIC MOTORCONSTRUCTION [75] Inventor: Jules Wisniewski, Cliffside Park,

[73] Assignee: Simmonds Precision Products, Inc.,

Tarrytown, N .Y.

22 Filed: Nov. 24, 1971 21 Appl. No.: 201,639

2,107,899 2/1938 Mueller ..310/241 2,105,926 H1938 Mueller.... ..310/2413,365,597 l/l968 Hanyu ..310/43 3,463,951 8/ 1969 Bauerle ..3 l0/89Primary Examiner-R. Skudy Attorney-Edwin E. Greigg 5 ABSTRACT Thisinvention relates to brush actuating mechanisms for direct currentmotors and, more particularly, to an innnovative plastic-molded housingfor these motors. The invention discloses a plastic-molded housing,closed at one end and apertured at the other end, said closed end havingopposed longitudinal recesses for receiving a brush, a cam lever, and ahelical spring,

[56] References Cited respectively therein, positively retained by anend UNITED STATES PATENTS cover slipped over said closed end and securedthereto, while said apertured end provides for the in- 3,525,891 8/1970Lukawich ..310/239 nior of permanent magnets and a driven shaft car-2,286,993 6/ 1942 Naul ..310/43 tying an armature, and commutator,2,775,717 12/1956 Laing ...3l0/246 3,173,044 3/1965 Pittman ..310/43 9Claims, 3 Drawing Figures 20 i e 28 I y v, V 26 4 g I 3 46 Patnted May22, 1973 ELECTRIC MOTOR CONSTRUCTION This invention relates to brushactuating mechanisms for direct current motors and, more particularly,to a plastic molded housing for direct current motors.

Generally, electric motors are comprised of a multiplicity of. partswhich require the time of a skilled craftsman for their assembly andmaintenance. These electric motors are further characterized in thatthey are not particularly reliable. Known motor structures of thisgeneral type are short lived primarily because of bearing failure whichis most frequently caused by carbon dust contamination due to a wearingaway of the brushes against the armature.

It is an object of this invention to provide a plastic molded housingwhich will allow for the elimination of many parts which normally haveonly a secondary function in existing design motors.

It is a further object of the invention to provide an ease of assemblyand maintenance of the motor by one other than a skilled craftsman.

It is a still further object of the invention to provide a novel brushassembly which will function with an efficiency equal to that ofexisting designs, however, with a much greater length of life byminimizing the wear of the brushes and therefore generally increasingthe reliability of the product.

The invention accordingly comprises features of construction,combinations of elements, the arrangements of parts which will beexemplified in the construction hereinafter set forth, and in the scopeof the application which will be indicated in the claims.

The invention will be better understood, as well as further objects andadvantages of the invention will become more apparent from the ensuingdetailed specification ofa preferred, although exemplary, embodimenttaken in conjunction with the drawing wherein:

FIG. 1 is a horizontal cross sectional view of an electric motor showingsome of the elements in elevation;

FIG. 2 is an isometric view of a plastic molded housing clearly showingthe critical cooperative elements according to the invention; and

FIG. 3 is a top plan view of the brush actuating mechanism according tothe invention.

' Referring now to the drawings, FIG. 1 shows a plastic housing 2constructed in a known manner, such as by blow molding incorporatingmolded-in permanent magnets l0 as shown, said housing having a closedend 13 and an oppositely disposed open end 15, the open end of thehousing being designed to be enclosed by an end plate 4 to be furtherdescribed below. With the electric motor design revealed in thisapplication, it will be seen that the assembly of substantially all ofits elements is achieved by being inserted through the open end 15.

The bearing comprising races 24, 26 and carrying balls 30 is insertedinto the cavity 17 in the closed end of the housing, as shown. Anarmature 12 provided with a commutator 14 of a conventional type andincluding oppositely extending shafts 18, 18' is inserted through theopen end of the housing, the end 18 of said shaft being mounted in ajournal aperture in said race 24 with the end of the shaft furthercarrying spacer means 19 designed to prevent longitudinal movement ofthe shaft assembly. A second bearing means having an outer race 20 andan inner race 22 is provided with balls 28 and with the journal aperture21' designed to support the other end 18 of said shaft passing throughsaid race. The armature assembly is further designed to be retained fromlongitudinal movement by a spacer means 21 positioned on the shaftbetween the armature and the inner end wall of the race 22, said raceassembly being retained in an aperture in the end plate 4 which enclosesthe open end of said housing subsequent to assembly of the elements ofsaid electric motor therewithin. The end plate 4 is fixed to saidhousing via two screws 8 (one shown), these being arranged to passthrough the housing into said end plate and secured therein prior toassembly of the cover 6 which will be referred to later herein.

With the exception of the novel plastic molded housing, the descriptionup to this point has been with regard to a substantially conventionalelectric motor. The novelty of the instant invention will becomeobvious, however, in the succeeding description of the final assembly ofan electric motor according to the invention.

The brush pigtails, not shown, are crimped or soldered to each of theterminals 42, at which time the brushes 16 are inserted into one of apair of guide means 38 provided in opposite relation in the housingadjacent to the closed end thereof, all of which is well shown in FIGS.2 and 3. The lever means 32 are then placed in the guide means 38 sothat the pivotal end 36 of the lever 32 rests on the brush 16. At theopposite extremity from said end 36 of the lever means 32, there isprovided a trunnion means 34 permitting pivotal movement thereof on ashelf portion 35 which is provided in said guide means 38.

A protuberance means 37 is provided adjacent to the pivot means 34 onthe lever means 32 and is designed to receive the lower extremity of acompression spring member 40 with its contour being complemental to thewalls provided in the housing and thereby arranged to retain the springin a plane normal to the longitudinal extent of said lever means.

It is believed to be now clear from the foregoing that by manuallyretaining the two springs 40 within the guide means, and havingpreviously secured the end plate in position, as explained earlier, anend cover 6 is slid over the closed end of the housing 2 to fullyenclose the guide means in positive planar juxtaposition with theperiphery of the housing 2. whereupon a suitable tape-like seal meansmay be placed about the circumference of the joint between the end cover6 and the housing 2.

FIG. 2 shows an isometric view of the plastic molded housing, followingthe invention, a portion of which is cut away in the area of the guidemeans 38 and 38 to show interior detail. The cutaway shows the generalshape and longitudinal extent of the guide means 38, extending from theshelf portion at the rear toward the terminal means at the front. Thisfigure well illustrates one of a pair of apertures through which screws8 are inserted to secure the end cover 6 to the housing 2. Also visibleis one of a pair of apertures 47 through which screws 8 are inserted tosecure end plate 4 to housing 2. The pair of terminals 42 by which powerconnections are made are also readily visible.

FIG. 3 shows in top plan the assembly of the lever means 32 in the guidemeans therefor and clearly illustrates the trunnions 34. This view alsoshows the lever means as well as the oppositely offstanding bosses 34with the opposite extremity 36 of the lever means in engagement with andurging the brush toward the commutator. Adjacent to the bosses, there isformed an upstanding protuberance 37 designed to cooperate with thehelically coiled spring 40 in order to retain said spring in a planenormal to the longitudinal extent of said lever means and consequentlyurge the brush toward the commutator.

The design of the lever means was particularly chosen such that themeasured change in the spring length is of a substantially lower ratiothan the decrease in the brush length due to wear, resulting in aninsignificant change of force upon the brush. Further, this designallows a spring of higher rate to be installed in the housing avoidingthe troublesome design of previous units known in the art which havevery small rate soft spring" designs that so often are the cause ofbrush hang up. The combination of a cam, as has been described, and aspring of a chosen rate allows the application of a proper force in psito be exerted on the brush. The choice of and the maintenance of theproper spring force as exerted on the brush is most important to theabove indicated goal of a long brush life. Evidence exists by way ofprototype tests that the long brush life desired has been achieved. Intests of three prototypes, the first unit tested had a brush life ofover 2,200 hours, the second had a brush life substantially over 3,500hours, while the third had a brush life in excess of 4,000 hours.

Since certain variations may be made in the preceding construction anddifferent embodiments of the invention could be made without departingfrom the scope thereof, it is intended that all matter contained in theforegoing description and shown in the attached figures shall beinterpreted as illustrative and not limitmg.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed and all statements as to the scope of the invention which, asa matter of language, might be said to fall therebetween.

What is claimed is:

1. In an electric motor having an armature and associated commutator andbrushes, the combination comprising,'a one-piece closed end housingserving to support one end of the bearing carrying shaft of thearmature, end plate means adapted for association with the other end ofsaid housing, said end plate means including further bearing meansserving to support the other end of said armature shaft, plurallongitudinally spaced oppositely disposed guide means integral with saidhousing, the first of said guide means serving to support the brushesand the second of said guide means serving to support pivotally mountedspring urged lever means having a longitudinal extent and spanning saidplural guide means.

2. In an electric motor as claimed in claim 1, wherein the second guidemeans includes a shelf portion adapted to receive the pivotal levermeans.

3. In an electric motor as claimed in claim 1, wherein the pivotal levermeans include means cooperative with said spring for retaining the samein a plane normal to the longitudinal extent of said lever means.

4. In an electric motor as claimed in claim 1, wherein a shell portionencompasses the closed end of said housing.

5. In an electric motor as claimed in claim 4, wherein the shell portionincludes an axial aperture.

6. In an electric motor as claimed in claim 4, wherein the shell portionretains the spring in engagement with the lever means.

7. In an electric motor as claimed in claim 4, wherein the shell portionincludes a terminal flange portion, said terminal flange portion beingarranged to be sealed to said housing.

8. In an electric motor as claimed in claim 1, wherein the longitudinalextent of said lever means lies in at least two distinct planes.

9. In an electric motor as claimed in claim 8, wherein the two distinctplanes are parallel.

1. In an electric motor having an armature and associated commutator andbrushes, the combination comprising, a one-piece closed end housingserving to support one end of the bearing carrying shaft of thearmature, end plate means adapted for association with the other end ofsaid housing, said end plate means including further bearing meansserving to support the other end of said armature shaft, plurallongitudinally spaced oppositely disposed guide means integral with saidhousing, the first of said guide means serving to support the brushesand the second of said guide means serving to support pivotally mountedspring urged lever means having a longitudinal extent and spanning saidplural guide means.
 2. In an electric motor as claimed in claim 1,wherein the second guide means includes a shelf portion adapted toreceive the pivotal lever means.
 3. In an electric motor as claimed inclaim 1, wherein the pivotal lever means include means cooperative withsaid spring for retaining the same in a plane normal to the longitudinalextent of said lever means.
 4. In an electric motor as claimed in claim1, wherein a shell portion encompasses the closed end of said housing.5. In an electric motor as claimed in claim 4, wherein the shell portionincludes an axial aperture.
 6. In an electric motor as claimed in claim4, wherein the shell portion retains the spring in engagement with thelever means.
 7. In an electric motor as claimed in claim 4, wherein theshell portion includes a terminal flange portion, said terminal flangeportion being arranged to be sealed to said housing.
 8. In an electricmotor as claimed in claim 1, wherein the longitudinal extent of saidlever means lies in at least two distinct planes.
 9. In an electricmotor as claimed in claim 8, wherein the two distinct planes areparallel.